1. Field of the Invention
The present invention relates to a wide band, large dynamic range magnetostatic delay line current sensor operable in the range from d.c. to several gigahertz having a high current sensitivity for a minimal detectable current in the order of 0.1 milliamps; specifically. High power, local, and remote current detection embodiments are also disclosed.
2. Description of the Prior Art
The invention described utilizes the high sensitivity of the magnetic spin wave phase with respect to changes in the biasing magnetic field producing a high sensitivity large bandwidth current sensor.
The magnetostatic wave delay lines based on ferrites having traveling wave propagation characteristics, for example, yttrium-iron garnet thin films (YIG) are microwave magnetic devices in which the electromagnetic energy couples through simple microstrip transducers into the magnetic properties of the material exciting a magnetic moment wave, or magnetostatic spin wave (MSW).
Important properties of a MSW delay line are the insertion loss, the wavenumber and the group delay and their evolution with frequency. These parameters are significant within the limited range of frequencies over which a MSW delay line operates. This frequency range or bandwidth is centered on a frequency, typically between 0.5 and 20 GHz, which depends on the strength of the applied magnetic bias field. The actual MSW delay line properties and bandwidth depend on design parameters such as ferrite film thickness, transducer width and distance from the ferrite to any ground planes above and below it.
The insertion loss is the loss of electromagnetic energy experienced between the input and the output of the device as a result of inefficient transducer operation and magnetic losses in the ferrite material. Typically, the insertion loss is lowest at the lower end of the frequency range of operation, increasing monotonically at higher frequencies. Typical minimum insertion losses are between 10 and 20 dB.
Magnetostatic waves have the property of being dispersive, that is, their propagation phase constant, or wavenumber, increases nonlinearly from zero to infinity over the frequency range over which MSWs can be launched. This dispersivity also depends on the design parameters described above.
The group delay is a measure of the time it takes for energy to travel between input and output transducers. It varies with frequency over the range of the device and its variation and absolute value depend also on the design parameters.
The problem to be solved then is the local and remote sensing in high electrical power systems as well as testing of an electronic printed circuit boards utilizing magnetostatic wave delay lines which are well known and can be commonly fabricated.